共查询到20条相似文献,搜索用时 7 毫秒
1.
Physiological and biochemical modifications induced by Fe-deficiency have been studied in cucumber ( Cucumis sativus L. cv. Marketer) roots, a Strategy I plant that initiates a rapid acidification of the medium and an increase in the electric potential difference when grown under Fe-deficiency. Using the aqueous two-phase partitioning method, a membrane fraction which has the plasmalemma characteristics was purified from roots of plants grown in the absence and in the presence of iron. The plasma membrane vesicles prepared from Fe-deficient plants showed an H+ -ATPase activity (EC 3.6.1.35) that is twice that of the non-deficient control. Furthermore, membranes from Fe-deficient plants showed a higher capacity to reduce Fe3+ -chelates. The difference observed in the reductase activity was small with ferricyanide (only 30%) but was much greater with Fe3 -EDTA and Fe3 -citrate (210 and 250%, respectively). NADH was the preferred electron donor for the reduction of Fe3+ compounds. Fe3+ reduction in plasma membrane from cucumber roots seems to occur with utilisation of superoxide anion, since addition of superoxide dismutase (SOD; EC 1.15.1.1) "in vitro" decreased Fe3+ reduction by 60%.
The response and the difference induced by iron starvation on these two plasma membrane activities together with a possible involvement of O2 in controlling the Fe3+ /Fe2+ ratio in the rhizosphere are discussed. 相似文献
The response and the difference induced by iron starvation on these two plasma membrane activities together with a possible involvement of O
2.
Enzymatic desulfurization of dibenzothiophene by a cell-free system of Rhodococcus erythropolis D-1 总被引:1,自引:0,他引:1
Abstract Pseudomonas syringae cells were exposed to Cu2+ alone or in the precence of acetate, proline or cysteine, at concentrations that reduced free Cu2+ to 1/10 of the total copper. Ligand concentrations (designated as isoeffective) were determined experimentally using a Cu2+ -selective electrode and confirmed by computer calculations using published stability constants. Exposure of P. syringae cells to Cu2+ alone resulted in rapid and pronounced cell death, and binding of most of the copper in solution. The addition of acetate, proline or cysteine, a few minutes after Cu2+ treatment, resulted in a significant reduction in cell death, and in the amount of copper bound to the cells. For short exposures to Cu2+ , cysteine was more effective than acetate or proline, but after 60 min of treatment, similar results were observed with these ligands. The addition of ligands before Cu2+ resulted in even more reduced copper toxicity. The results showed that, at isoeffective concentrations, weak and moderate copper-ligands can effectively antagonize copper toxicity, and that this protective effect does not require previously equilibrated copper-ligand solutions and is not very dependent of the nature of the ligand. 相似文献
3.
Abstract— Myelin, synaptosomal and mitochondrial fractions obtained from homogenates of whole mouse brain contain K+ which can exchange with 42 K+ at 2º in 0·32 m -sucrose. The content and rates of exchange of K+ were greater at pH 8·2 than at 6·1. In the synaptosomal preparations, the rates of exchange and content of 42 K+ and K+ declined progressively with decreasing pH.
Of the total synaptosomal K+ , 95 per cent could exchange with external 42 K+ . At pH 7·5, 20 per cent of the K+ and 78 per cent of the Na+ appeared to reside in osmotically insensitive pools. Synaptosomal K+ at 2º was slowly displaced by NaCl (0·18 m ) and the rate of exchange between 42 K+ and K+ was retarded. KCI (0·18 m ) did not readily displace endogenous Na+ . Synaptosomal K+ exchanged with exogenous K+ more rapidly than with exogenous Na+ .
These observations have been discussed in terms of possible roles for ion exchange as the principal means by which K+ traverses the plasma membrane at 2º. 相似文献
Of the total synaptosomal K
These observations have been discussed in terms of possible roles for ion exchange as the principal means by which K
4.
Effects of mixtures of chloride salts of cadmium, copper and zinc on survival, whole body residues, and histopathology of mummichog, Fundulus heteroclitus (L.), were investigated in synthetic sea water at 20‰ salinity and 20°C. Mixtures of Cu2+ and Zn2+ as indicated by 96 h bioassay studies produced more deaths than expected on the basis of toxicities of individual components. Concentrations of Cd2+ not ordinarily lethal exerted a negative effect on survival of fish intoxicated by salts of copper, zinc, or both.
Atomic absorption determinations of Cd, Cu, and Zn residues in mummichog which survived 96 h exposures to each of these toxicants provided useful indices of total body burdens for these metals. Residues from survivors held in mixtures, especially Cd2+ and Zn2+ mixtures, did not conform to patterns observed for single elements. Whole body aggregates of Cd, Cu, and Zn from dead mummichogs were of limited worth owing to possible accumulation of these metals from the medium after death.
Renal and lateral line canal lesions were noted in all fish subjected to copper concentrations of 1 mg/1 and higher. Renal lesions observed in fish immersed in mixtures of Cu2+ and Cd2+ assumed a damage pattern characteristic of Cd2+ ; with mixtures of Cu2+ and Zn2+ , lesion were typical of Cu2+ -induced damage. Lesions induced in lateral line epithelium by Cu2+ were not affected by either Cd2+ or Zn2+ . Epithelia lining the oral cavity were necrotized by the caustic action of high levels of Zn2+ (60 mg/1) and of Cu2+ (8 mg/1). 相似文献
Atomic absorption determinations of Cd, Cu, and Zn residues in mummichog which survived 96 h exposures to each of these toxicants provided useful indices of total body burdens for these metals. Residues from survivors held in mixtures, especially Cd
Renal and lateral line canal lesions were noted in all fish subjected to copper concentrations of 1 mg/1 and higher. Renal lesions observed in fish immersed in mixtures of Cu
5.
New insights into the metal specificity of the Pseudomonas aeruginosa pyoverdine–iron uptake pathway
Armelle Braud Françoise Hoegy Karine Jezequel Thierry Lebeau Isabelle J. Schalk 《Environmental microbiology》2009,11(5):1079-1091
Pyoverdine (PvdI) is the major siderophore secreted by Pseudomonas aeruginosa PAOI in order to get access to iron. After being loaded with iron in the extracellular medium, PvdI is transported across the bacterial outer membrane by the transporter, FpvAI. We used the spectral properties of PvdI to show that in addition to Fe3+ , this siderophore also chelates, but with lower efficiencies, all the 16 metals used in our screening. Afterwards, FpvAI at the cell surface binds Ag+ , Al3+ , Cd2+ , Co2+ , Cu2+ , Fe3+ , Ga3+ , Hg2+ , Mn2+ , Ni2+ or Zn2+ in complex with PvdI. We used Inductively Coupled Plasma-Atomic Emission Spectrometry to monitor metal uptake in P. aeruginosa : TonB-dependent uptake, in the presence of PvdI, was only efficient for Fe3+ . Cu2+ , Ga3+ , Mn2+ and Ni2+ were also transported into the cell but with lower uptake rates. The presence of Al3+ , Cu2+ , Ga3+ , Mn2+ , Ni2+ and Zn2+ in the extracellular medium induced PvdI production in P. aeruginosa . All these data allow a better understanding of the behaviour of the PvdI uptake pathway in the presence of metals other than iron: FpvAI at the cell surface has broad metal specificity at the binding stage and it is highly selective for Fe3+ only during the uptake process. 相似文献
6.
Comparative studies of inorganic substances in the blood of fishes from the Scagerac Sea 总被引:1,自引:0,他引:1
The concentrations of the main plasma inorganic electrolytes Na+ , K+ , Ca2+ , Mg2+ , Cl- and and PO4 3- have been determined for different orders of marine fishes. For Na+ and Cl- a typical decrease was found when passing from cyclostomes, holocephalans and elasmobranchs to teleosts. The concentrations of K+ , Ca2+ and Mg2+ showed a similar trend except that there was a rise in the teleost group, which showed a large range of variation for these three ions. In the case of PO4 3- no significant differences between groups were found. 相似文献
7.
Indispensability of Iron for the Growth of Cultured Chick Cells 总被引:1,自引:0,他引:1
KOJI SAITO YASUKO HAGIWARA TAKAYUKI HASEGAWA EIJIRO OZAWA 《Development, growth & differentiation》1982,24(6):571-580
In order to clarify the role of iron in the growth promoting effect of transferrin (Tf), the effects of the following substances were examined in cultured chick skeletal myogenic cells: transition metal ions (Fe2+ , Fe3+ , Cr3+ , Cu2+ , Mn2+ , Co2+ , Cd2+ , Zn2+ and Ni2+ ), Tf complexes with these metals and metal-free apoTf.
The cells did not grow well when incubated in a culture medium composed of Eagle's minimum essential medium and horse serum. But they grew well in the presence of Fe2+ or Fe3+ (10–100 μM) or iron-bound Tf (10–500 nM) in the medium. None of the transition metal ions other than iron was effective. Neither apoTf nor Tf complexes with these metals showed the growth promoting effect. The generality of the requirement of iron for cell growth was ascertained in the primary culture of other types of chick embryonic cells: fibroblasts, cardiac myocytes, retinal pigment cells and spinal nerve cells.
The results show that iron is one of the indispensable substances for cell growth and suggest that Tf protein plays a role in facilitating the transport of iron into the cells. 相似文献
The cells did not grow well when incubated in a culture medium composed of Eagle's minimum essential medium and horse serum. But they grew well in the presence of Fe
The results show that iron is one of the indispensable substances for cell growth and suggest that Tf protein plays a role in facilitating the transport of iron into the cells. 相似文献
8.
YIYONG ZHU TINGJUN DI GUOHUA XU XI CHEN HOUQING ZENG FENG YAN & QIRONG SHEN 《Plant, cell & environment》2009,32(10):1428-1440
The preference of paddy rice for NH4 + rather than NO3 - is associated with its tolerance to low pH since a rhizosphere acidification occurs during NH4 + absorption. However, the adaptation of rice root to low pH has not been fully elucidated. This study investigated the acclimation of plasma membrane H+ -ATPase of rice root to low pH. Rice seedlings were grown either with NH4 + or NO3 - . For both nitrogen forms, the pH value of nutrient solutions was gradually adjusted to pH 6.5 or 3.0. After 4 d cultivation, hydrolytic H+ -ATPase activity, V max , K m , H+ -pumping activity, H+ permeability and pH gradient across the plasma membrane were significantly higher in rice roots grown at pH 3.0 than at 6.5, irrespective of the nitrogen forms supplied. The higher activity of plasma membrane H+ -ATPase of adapted rice roots was attributed to the increase in expression of OSA1, OSA3, OSA7, OSA8 and OSA9 genes, which resulted in an increase of H+ -ATPase protein concentration. In conclusion, a high regulation of various plasma membrane H+ -ATPase genes is responsible for the adaptation of rice roots to low pH. This mechanism may be partly responsible for the preference of rice plants to NH4 + nutrition. 相似文献
9.
The toxicity of iron to brown trout and effects on the gills: a comparison of two grades of iron sulphate 总被引:3,自引:0,他引:3
The 96-h LC50 on brown trout Salmo trutta of a commercial iron (III) sulphate liquor, used for treating reservoirs to reduce algal growth, was 28 mg total Fe l−1 (0·05 mg soluble Fe l−1 ). The 96-h LC50 for analar grade iron (III) sulphate was 47 mg total Fe l−1 (0·24 mg soluble Fe l−1 ). Lethal and sublethal exposure to both grades of iron resulted in accumulation on the gill, which appears to be the main target for iron toxicity. Greater iron accumulation occurred during exposure to commercial iron sulphate liquor. Physical clogging of gills and gill damage was seen during lethal and sublethal exposure to iron. Gill tissue analysis showed no evidence of iron uptake into gill tissues during lethal or sublethal exposure to iron. Iron did not accumulate in plasma of fish exposed to iron compared to controls. Respiratory disruption due to physical clogging of the gills is suggested as a possible mechanism for iron toxicity. 相似文献
10.
Approximation of the total escape area of the xylem in an inbred line of tomato (Ly-copersicon escutentum Mill. cv. Tiny Tim) with help of the frequency distribution of xylem vessel radii provides the possibility to calculate realistic escape constant values from uptake experiments of several elements into tomato stem segments. Comparison of the lateral escape rates of 24 Na+ , 42 K+ , 86 Rb+ and 134 Cs+ indicate that Na+ escape is rate-limited by its uptake into a rather constant number of surrounding cells, regardless of changes in the total escape area of the xylem vessels. The escape of K+ , Rb+ and Cs+ seems to be proportional to the surface area of the xylem vessels and their escape is apparently controlled by their transport across the cell walls of the transport channels. The calculated small values for the escape rate constants (apparent permeability of the xylem cell walls, ca 2–3 · 10−9 m s−7 ) are probably due to the presence of lignin in the xylem cell walls, the discrimination between ions as a result of differing affinities and selectivities and the presence of other solutes in the applied solution. 相似文献
11.
Salts at high concentrations may cause oxidative damage to plant cells since many studies indicated the involvement of reactive oxygen species in salt-stress response. Recently, we have demonstrated that treatment of tobacco ( Nicotiana tabacum ) cell suspension culture with various salts result in an immediate burst of superoxide production via activation of NADPH oxidase by ions of alkali metals (Li+ , Na+ , K+ ), alkali earth metals (Mg2+ , Ca2+ ) or lanthanides (La3+ , Gd3+ ). In this study, we tested the effect of extracellular supplementation of Zn2+ and Mn2+ on the cation-induced oxidative burst in tobacco cell suspension culture, measured with a superoxide-specific Cypridina luciferin-derived chemiluminescent reagent. Extracellular supplementation of Zn2+ and Mn2+ inhibited the generation of superoxide in response to addition of salts. Although both Zn2+ and Mn2+ inhibited the salt-induced generation of superoxide, the modes of inhibition by those ions seemed to be different since Mn2+ simply inhibited total production of superoxide while Zn2+ inhibited the early phase of superoxide production and induced the slow release of superoxide. Roles of Mn2+ and Zn2+ in protection of plant cells from salt stress, as an effective superoxide scavenger and an effective inhibitor of plasma membrane-bound NADPH oxidase, respectively, are discussed. 相似文献
12.
Effective regulation of iron acquisition in graminaceous plants. The role of mugineic acids as phytosiderophores 总被引:6,自引:0,他引:6
Discovery of mugineic acids as phytosiderophores has shown that some graminaceous monocotyledonous plants have a different iron acquisition strategy (strategy II) from dicotyledonous and nongraminaceous monocotyledonous plants (strategy I). The process of iron acquisition by strategy II plants can be divided into four main steps: biosynthesis, secretion, solubilization, and uptake, all of which are effectively regulated by different systems. The biosynthesis of mugineic acids is controlled by an on-off system which is operated under the control of iron demand in the plant. All mugineic acids share the same biosynthetic pathway from L-methionine to 2'-deoxymugineic acid, but the subsequent steps differ among plant species and even cultivars. The biosynthesis of mugineic acids is associated with the methionine recycling pathway. The secretion of mugineic acids shows a distinct diumal rhythm. Mugineic acids solubilize sparingly soluble inorganic iron by chelation and possess a high chelation affinity for iron, but not for other polyvalent ions such as Ca2+ , Mg2+ and Al3+ . The iron uptake process is regulated by a specific uptake system that transports the mugineic acid-Fe(III) complex as an intact molecule. This system specifically recognizes the mugineic acid-Fe(III) complexes, but not other mugineic acid-metal or synthetic chelator-Fe(III) complexes, suggesting that binding sites with strict recognition for stereostructure of the complex are located on the plasma membrane. All these regulatory systems are considered to represent an efficient strategy to acquire adequate amounts of iron and to avoid factors unfavorable for iron acquisition such as high pH, high concentrations of bicarbonate, Ca2- and Mg2+ , microbial degradation, and uptake of other metals that are common in calcareous soils. 相似文献
13.
M. Santiago E. R. Matarredona L. Granero J. Cano A. Machado 《Journal of neurochemistry》1997,68(2):732-738
Abstract: Microdialysis was used to evaluate the effect of desferrioxamine (DES) against 1-methyl-4-phenylpyridinium (MPP+ ) toxicity. The presence of DES (40 fmol-40 nmol/15 min for a total of 90 min) in the Ringer solution, coperfused with MPP+ (40 nmol/15 min) on day 1, produced on day 2 a higher extracellular dopamine output after perfusion of MPP+ than in control MPP+ perfusion experiments, in which no DES was administered on day 1. Both Ringer perfusion alone (control Ringer) and coperfusion of 40 nmol DES with 40 nmol MPP+ on day 1 produced on day 2 similar increases in extracellular dopamine output after a second MPP+ perfusion. In the control Ringer experiment, note that the MPP+ on day 2 is the first MPP+ perfusion. Perfusion of 800 fmol FeCl3 /15 min along with 40 nmol MPP+ and 400 fmol DES on day 1 completely abolished on day 2 the neuroprotective effect found with 40 nmol MPP+ and 400 fmol DES; 800 fmol FeCl3 did not increase the neurotoxic effect of 40 nmol MPP+ perfusion. The ability of DES to protect against MPP+ toxicity may indicate a therapeutic strategy in the treatment of diseases when iron is implicated. 相似文献
14.
Abstract: Zinc-65 transport into different regions of rat brain has been measured during short vascular perfusion of one cerebral hemisphere with an oxygenated HEPES-containing physiological saline at pH 7.40. The [Zn2+ ] was buffered with either bovine serum albumin or histidine. In each case uptake was linear with time up to 90 s. 65 Zn flux into brain in the presence of albumin followed Michaelis-Menten kinetics and for parietal cortex had a K m of 16 n M and a V max of 44 nmol/kg/min. Increasing concentrations of l -histidine enhanced 65 Zn flux into brain at [Zn2+ ] values between 1 and 1,000 n M . The combined effect of [histidine] and [Zn2+ ] was best accounted for by a function of [ZnHis+ ], i.e., flux = 64.4 · [ZnHis+ ]/(390 + [ZnHis+ ]) + 0.00378 · [ZnHis+ ], with concentrations being nanomolar. d -Histidine had an influence similar to that of l -histidine. 65 Zn flux in the presence of 100 µ M l -histidine was not affected by either 500 µ M l -arginine or 500 µ M l -phenylalanine. The results indicate specific transport of Zn2+ across the plasma membranes of brain endothelium. The enhancement due to histidine has been attributed to diffusion of ZnHis+ across unstirred layers "ferrying" zinc to and from transport sites. 相似文献
15.
Activity of methanotrophic bacteria in Green Bay sediments 总被引:3,自引:0,他引:3
Lorie A. Buchholz J.Val Klump Mary Lynne Perille Collins Christine A. Brantner Charles C. Remsen 《FEMS microbiology ecology》1995,16(1):1-8
Abstract Sediment pore water samples obtained from a 19 m station in Green Bay in Lake Michigan were examined for levels of ambient dissolved methane and copper, and for the potential for in situ methane oxidation by methanotrophs found within surface sediments. The in situ methane concentration in the upper oxic sediment layer ranged from 20–150 μmol · 1−1 at this station. The activity of methanotrophs and the kinetics of methane oxidation in these sediments were demonstrated by the uptake of radiolabeled methane. Ks values varied between 4.1–9.6 nmol · cm3 of sediment slurry. High Vmax values (12.7–35.2 nmol · cm−3 · h−1 ) suggest a large population of methanotrophs in the sediments. An average methane flux to the oxic sediments of 0.24 mol · m−2 · year−1 was calculated from the pore water methane gradients. Pore water concentrations of copper in the upper sediment layer ranged from 10–120 nmol · 1−1 . Based upon the copper concentration, other measured parameters, and equilibrium conditions defined by WATEQF4, an estimate for dissolved free Cu2+ concentration of 5–38 nmol · 1−1 pore water was obtained. Several factors control the rate of methane oxidation, including oxygen, methane, and the bioavailability of free Cu2+ . 相似文献
16.
Free cytosolic Ca2+ ([Ca2+ ]cyt ) is an ubiquitous second messenger in plant cell signaling, and [Ca2+ ]cyt elevation is associated with Ca2+ -permeable channels in the plasma membrane and endomembranes regulated by a wide range of stimuli. However, knowledge regarding Ca2+ channels and their regulation remains limited in planta . A type of voltage-dependent Ca2+ -permeable channel was identified and characterized for the Vicia faba L. guard cell plasma membrane by using patch-clamp techniques. These channels are permeable to both Ba2+ and Ca2+ , and their activities can be inhibited by micromolar Gd3+ . The unitary conductance and the reversal potential of the channels depend on the Ca2+ or Ba2+ gradients across the plasma membrane. The inward whole-cell Ca2+ (Ba2+ ) current, as well as the unitary current amplitude and NPo of the single Ca2+ channel, increase along with the membrane hyperpolarization. Pharmacological experiments suggest that actin dynamics may serve as an upstream regulator of this type of calcium channel of the guard cell plasma membrane. Cytochalasin D, an actin polymerization blocker, activated the NPo of these channels at the single channel level and increased the current amplitude at the whole-cell level. But these channel activations and current increments could be restrained by pretreatment with an F-actin stabilizer, phalloidin. The potential physiological significance of this regulatory mechanism is also discussed. 相似文献
17.
Transport interactions between cadmium and zinc in roots of bread and durum wheat seedlings 总被引:24,自引:0,他引:24
Field studies have shown that the addition of Zn to Cd-containing soils can help reduce accumulation of Cd in crop plants. To understand the mechanisms involved, this study used 109 Cd and 65 Zn to examine the transport interactions of Zn and Cd at the root cell plasma membrane of bread wheat ( Triticum aestivum L.) and durum wheat ( Triticum turgidum L. var. durum ). Results showed that Cd2+ uptake was inhibited by Zn2+ and Zn2+ uptake was inhibited by Cd2+ . Concentration-dependent uptake of both Cd2+ and Zn2+ consisted of a combination of linear binding by cell walls and saturable, Michaelis-Menten influx across the plasma membrane. Saturable influx data from experiments with and without 10 µm concentrations of the corresponding inhibiting ion were converted to double reciprocal plots. The results revealed a competitive interaction between Cd2+ and Zn2+ , confirming that Cd2+ and Zn2+ share a common transport system at the root cell plasma membrane in both bread and durum wheat. The study suggests that breeding or agronomic strategies that aim to decrease Cd uptake or increase Zn uptake must take into account the potential accompanying change in transport of the competing ion. 相似文献
18.
Lobão FA Façanha AR Okorokov LA Dutra KR Okorokova-Façanha AL 《FEMS microbiology letters》2007,274(1):17-23
The effect of aluminum on dimorphic fungi Yarrowia lipolytica was investigated. High aluminum (0.5–1.0 mM AlK(SO4 )2 ) inhibits yeast–hypha transition. Both vanadate-sensitive H+ transport and ATPase activities were increased in total membranes isolated from aluminum-treated cells, indicating that a plasma membrane H+ pump was stimulated by aluminum. Furthermore, Al-treated cells showed a stronger H+ efflux in solid medium. The present results suggest that alterations in the plasma membrane H+ transport might underline a pH signaling required for yeast/hyphal development. The data point to the cell surface pH as a determinant of morphogenesis of Y. lipolytica and the plasma membrane H+ -ATPase as a key factor of this process. 相似文献
19.
Danish rainbow trout, Salmo gairdneri Richardson, (40–65 g) were transferred to 28%o sea water at intervals throughout the early spring and summer. Gill Na+ /K+ -ATPase of fish kept in fresh water surged distinctly during May. Simultaneously, a body silvering occurred and plasma concentrations of Cl− , Na+ and total thyroxine (T4) decreased. The seawater transfer-induced adaptive response in plasma electrolytes comprised a biphasic change, i.e., an adjustive peak phase and a regulatory phase lasting for 2 days and 1 week after transfer, respectively. Further, gill Na+ /K+ -ATPase activity increased to a new level after an initial lag phase of 2–3 days, but electrolyte regulation was mostly initiated prior to the adaptive change in ATPase activity. In spite of increasing pre-transfer freshwater Na+ /K+ -ATPase activity during the spring, the electrolyte peak level, the degree of muscle dehydration and the mortality of fish transferred to sea water increased from April to July. The apparent uncoupling of freshwater Na+ /K+ -ATPase activity and plasma electrolyte regulation in sea water is discussed in relation to smelting and prediction of hypo-osmoregulatory performance. 相似文献
20.
Increases in cytosolic free Ca2+ ([Ca2+ ]cyt ) are common to many stress-activated signalling pathways, including the response to saline environments. We have investigated the nature of NaCl-induced [Ca2+ ]cyt signals in whole Arabidopsis thaliana seedlings using aequorin. We found that NaCl-induced increases in [Ca2+ ]cyt are heterogeneous and mainly restricted to the root. Both the concentration of NaCl and the composition of the solution bathing the root have profound effects on the magnitude and dynamics of NaCl-induced increases in [Ca2+ ]cyt . Alteration of external K+ concentration caused changes in the temporal and spatial pattern of [Ca2+ ]cyt increase, providing evidence for Na+ -induced Ca2+ influx across the plasma membrane. The effects of various pharmacological agents on NaCl-induced increases in [Ca2+ ]cyt indicate that NaCl may induce influx of Ca2+ through both plasma membrane and intracellular Ca2+ -permeable channels. Analysis of spatiotemporal [Ca2+ ]cyt dynamics using photon-counting imaging revealed additional levels of complexity in the [Ca2+ ]cyt signal that may reflect the oscillatory nature of NaCl-induced changes in single cells. 相似文献